The IEEE 802.11n joint proposal group currently proposes using a hybrid space-time block code (STBC) and spatial division multiplexing (SDM) scheme for the next generation of high performance wireless networks. This hybrid STBC/SDM scheme results in unbalanced quality of service for data streams which translates into lower residual signal-to-noise ratio (SNR) at the output of a receiver. In conventional systems, equal MCSs are applied to all spatial streams. However, this results in a loss of benefits of the diversity gain for the spatial stream carried by STBC precoding.
Therefore, it would be desirable to provide a method and apparatus for applying unequal MCSs or stream-dependent MCSs while performing spatial processing, such as STBC.